The invention relates to synchronizing local clocks in a distributed computer network. Of particular interest are computer networks that exchange information via messages that are sent on communication links between components in the network. Without restriction to a specific realization of the invention we use standard Ethernet as an illustrating example. In standard Ethernet end systems are connected via network switches via bi-directional communication links. An end system will communicate with a second end system or a group of end systems via sending a message to the switch, which will then relay the message to the receiving end system or end systems. Likewise end systems can be connected directly to each other via bi-directional communication links, which makes a clear differentiation between end systems and switches in certain configurations difficult. Hence, generally we use the term component to refer to a physical device that can be either end system or switch. Whether a component is said to be an end system or said to be a switch is determined by its usage rather than its physical appearance.
The clock synchronization problem is the problem of bringing the local clocks of different components into close agreement. For fault-tolerance reasons a magnitude of components can be configured that generate synchronization messages.
The problem of synchronizing local clocks has a long history and many algorithms that claim synchronization of local clocks also in presence of failures are known (Byzantine clock synchronization, Lamport, L. and Melliar-Smith, P. M., ACM SIGOPS Operating Systems Review, volume 20, number 3, p. 10-16, 1986, ACM New York, N.Y., USA; Optimal clock synchronization, Srikanth, T K and Toueg, S., Journal of the ACM (JACM), volume 34, number 3, p. 626-645, 1987, ACM New York, N.Y., USA; A paradigm for reliable clock synchronization, Schneider, F. B., Department of Computer Science Technical Report TR, p. 86-735; Clock synchronization in distributed real-time systems, Kopetz, H. and Ochsenreiter, W., IEEE Transactions on Computers, volume 36, number 8, p. 933-940, 1987, IEEE Computer Society Washington, D.C., USA; Startup and Recovery of Fault-Tolerant Time-Triggered Communication: With a Focus on Bus-Based and Switch-Based Network Topologies, Steiner, W., 2008, Vdm Verlag Dr. Müller).